One day someone will look at the MAME source code and get the bill validator working properly, it's just one of those things where there is literally just one person in the whole world working on it, and only when there is another set of game chips to add. The reason the bill validator doesn't work these days is that the source code used to get it working was a fluke to begin with, and was later modified due to the original code making no sense at all (hence breaking it after 0.183).
Basically, a single line of code in peplus.cpp changed from:
return (0x70 || m_in0->read()); // Add Bill Validator Credit Pulse
to:
return (0x70 | m_in0->read()); // Add Bill Validator Credit Pulse
Replace the missing | (vertical bar) and it should theoretically work again (although I haven't tried in several years).
FWIW, a modern version of MAME can still be compiled manually with the old bill validator code re-added to the source; this will let you run the later dumps while still being able to feed the games with virtual $100 bills. One catch is, MAME's default compiler hasn't been compatible with Windows XP for several years, although you can apparently still make XP-compatible versions with other compilers if absolutely needed. In any case, I'd suggest upgrading the dinosaur to at least a Core 2 Duo with a modern 64-bit OS, as modern MAME performs terribly on Pentium 4 machines (aside from the mediocre CPU, the main bottleneck is weak AGP video cards, most of which do not support certain video card standards from circa 2010 that MAME uses these days).